Cerenkov and sub-Cerenkov radiation from a charged particle beam

Abstract
As a consequence of the relaxation of the phasing condition between the moving charge and radiated wave for finite beam path lengths, the Cerenkov peak is broadened and the threshold energy is lowered. A criterion for the threshold energy is developed which is applicable to charged beams consisting of a single charge bunch of finite size, as well as beams consisting of periodically repeated bunches.